1. Field of the Invention
The present invention relates to mobile chairs and, more particularly, to such chairs which are lockable in a stationary position.
2. Description of the Prior Art
One problem associated with currently available mobile chairs, such as wheel chair, swivel chair, rocking chair and swinging chair, is that they do not lock in position to provide a stable support to a person which attempts to rise from the chair or sit thereon. This problem is particularly important for people who must rely onto the strength of their arms in order to get up from the chair and take place thereon.
Accordingly, it has been proposed to provide such mobile chairs with manually operated locking systems. However, the user must remember to lock the chair in a stationary position before attempting to rise or before being transferred therefrom with the help of another person. If the user or the helper forgets to activate the locking system, the chair may move backward and cause the occupant to fall. This may result in serious injuries.
A number of inventions have been proposed to overcome this problem. For instance, U.S. Pat. No. 4,623,043 issued on Nov. 18, 1986 to Babilas, U.S. Pat. No. 4,320,818 issued on Mar. 23, 1982 to Knoche, U.S. Pat. No. 4,438,973 issued on Mar. 27, 1984 to Lapointe and U.S. Pat. No. 5,203,433 issued to Dugas on April 1993 all disclose an automatic immobilizing system having an actuator operative to automatically activate a braking mechanism when a chair occupant lift is weight from a seat portion of the chair or sufficiently displace his buttock towards the front of the seat portion.
Although the automatic brake mechanism disclosed in the above mentioned patents have a common objective of automatically locking the mobility functions of the chair when an occupant attempts to rise, they all necessitate that the occupant lift his weight from the seat of the chair or at least move his buttock forward to a fore part of the seat to effect locking of the mobility functions. The fact that the stabilization of the chair only occurs after the occupant has at least partly lifted is weight from the seat of the chair i.e. when he/she is no longer in a normal sitting position, may cause the chair to move backward as the occupant is attempting to rise from the chair and, thus, may result in various injuries.
Therefore, there is still a need for a self-locking mechanism which would allow to automatically lock the mobility functions of a chair when an occupant intends to rise from the chair without the occupant having to completely or partially remove is weight from the seat portion of the chair.
It is therefore an aim of the present invention to provide a self-locking chair which automatically locks in a stationary position when an occupant intends to rise from a sitting position.
It is also an aim of the present invention to provide an improved safety device for automatically locking the mobility functions of a chair when an occupant intends to rise therefrom.
Therefore, in accordance with the present invention there is provided a self-locking system for a chair of the type having a seat and mobility functions, the self-locking system comprising a lock displaceable between idle and functional positions for selectively locking the mobility functions of the chair, and a state selector for detecting the intent of an occupant to rise from the chair and then automatically causing the lock to move to its functional position, wherein said state selector is responsive to movement of an upper portion of the body of the occupant while the occupant is still supported in a normal seated position on the seat of the chair, thereby allowing the locking of the mobility functions of the chair to occur before the occupant starts to lift his weight from the seat of the chair.